The Bernie Sanders campaign's finances have come under scrutiny from the Federal Election Commission, according to a Sunday letter from the body to the campaign's treasurer.

The six-page letter requests more information from the campaign on 10 different items related to campaign finance regulations that appear to have been violated in the report. These include individual donations that appear to exceed contribution limits outlined by federal law, improper-looking donations from LLCs, a question about a contribution from someone with a non-U.S. mailing address, concerns about incorrect-looking totals, and other accounting problems

Following the letter, the commission listed 510 pages worth of "apparent excessive, prohibited, and impermissible contributions."

The letter gives the campaign until the end of March to respond to the commission's listed concerns, in order to determine whether the campaign will be audited or not. It also says that failure to comply may result in enforcement action against the campaign.

"Letters such as this aren't uncommon for large presidential campaigns," Center for Public Integrity editor-at-large Dave Levinthal explained on Twitter, "but this is still a lot."

While Sanders' campaign spending may be dwarfed along with the rest of the Democratic field by former New York City Mayor Michael Bloomberg's self-funded 2020 bid, the self-described democratic socialist is still out-fundraising his non-billionaire primary rivals.

Sanders wasn't alone in getting such a notice from the Federal Election Commission over the weekend, either. The Trump campaign also got a similar letter from the FEC with three listed items to respond to and 411 pages of "apparent excessive, prohibited, and impermissible contributions."

But regardless of what the responses to the letters are or whether the commission deems them adequate, the FEC's enforcement abilities are still severely hamstrung by a monthslong lack of a quorum, which raises the question of whether or not the federal body will actually be able to do if the deadline were to run out without any responses.